Material composition for packaging of light-sensitive components and method of using the same

ABSTRACT

The invention pertains to a material composition for packaging. The composition comprises (a) an epoxy resin and (b) a curing agent, wherein the mixing ratio of said epoxy resin to said curing agent is in the range of from 0.7 to 1.1. The invention also pertains to a method of using said material composition for packaging a light-sensitive component on a substrate.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a material composition and itsuse for the packaging of light-sensitive components.

[0003] 2. Description of the Prior Art

[0004] In view of the coming of digital age, light-sensitive componentshave been widely utilized in various electronic products. Particularly,the development of image sensors has progressed rapidly.

[0005] In general, a method for packaging an image sensor comprisesusing a mold compound to form a dam around each modular circuit by atransfer molding process; fixing an image sensor to the circuit by aconductive adhesive and accomplishing the wire bonding; applying anadhesive over the dam and placing a glass sheet on the adhesive; andcuring the adhesive. ROC Patent Publications No. 459355, 478136, 503574,and 501244 have disclosed packaging structures and methods of imagesensors.

[0006] In conventional processes, the light-transmission layer coveringimage sensor chips is normally glass, as disclosed in theabove-mentioned patent publications. This is because glass has lowrefractive indices, high light-transmission, and scratch resistance.However, in the processes utilizing light-transmission layers of glass,the chips can only be packaged one by one. Such packaging manner willconsume a larger amount of efforts and time, cannot achieve good yields,and is costly.

[0007] ROC Patent Publication No. 489532 describes a stacked structureof an image sensor. This patent publication also discloses utilizing amolding compound and transfer molding, but the light-transmission layerfor covering by molding is a transparent resin layer rather than a glasssheet, Nonetheless, said patent publication does not teach, disclose, orsuggest what the properties which the resin would possess are or whatthe effects which the resin would have on light are.

[0008] Although conventional epoxy resins with a benzene ring, such asbisphenol A epoxy resin, bisphenol F epoxy resin, and nathalene-typeepoxy resin, are transparent, the refractive indices of such resins uponcuring are all higher than 1.50. This is because when the visible lightpasses through a benzene ring, the unsaturated π bond of the benzenering will absorb the light to reduce a π−π* interaction and to alter therefractive indices and the light transmission rates. The use of thoseepoxy resins without any benzene rings may effectively reduce refractiveindices. However, such resins do not have the properties, such as highglass transition temperatures and heat resistance, that glass possesses.

[0009] The inventors of the subject application have found that thereare certain material compositions that are useful as encapsulatingmaterials for packaging, in particular, the packaging of image sensors.Such material compositions, after being cured, will provide theadvantages of high glass transition temperatures, low refractiveindices, high light transmission, and scratch resistance, and can beused in transparent layers and as substitutes for glass. When utilizingthe compositions of the present invention for packaging on a substrate,said compositions may be cured by heat and then the packaged substratecan be divided into single modules. Such packaging manner is simplerthan that for single chip when using glass, and will reduce productioncost and enhance production capacity and yield.

DESCRIPTION OF THE INVENTION

[0010] One of the objects of the invention is to provide a materialcomposition for packaging comprising (a) an epoxy resin and (b) a curingagent, wherein the mixing ratio of said epoxy resin to said curing agentis in the range of from 0.7 to 1.1.

[0011] One more object of the present invention is to provide a methodof using the above packaging material composition for packaginglight-sensitive components on a substrate.

[0012] The material composition for packaging of the present inventioncomprises (a) an epoxy resin and (b) a curing agent wherein the mixingratio of said epoxy resin to said curing agent is in the range of from0.7 to 1.1, preferably from 0.85 to 1.0.

[0013] There are no special requirements for the epoxy resins which canbe used in the present invention. Examples of useful epoxy resinsinclude bisphenol A epoxy resin, bisphenol F epoxy resin, an aliphaticepoxy resin, and a cycloaliphatic epoxy resin and a mixture thereof, ofwhich the aliphatic epoxy resin and cycloaliphatic epoxy resin are thepreferred epoxy resin. Non-limiting examples of suitable epoxy resinsinclude, for example, ERL-4221 and ERL-4229, commercially available fromDow Chemical; EPON 1510, Holxy Modifer 7, Holxy Modifer 8, Holxy Modifer61, Holxy Modifer 116, Holxy Modifer 48, Holxy Modifer 67, Holxy Modifer68, and Holxy Modifer 107, commercially available from Resolution; andEPICLON EXA-7015, EXA-7120, and EPICLON 726D, commercially availablefrom Dainippon Ink & Chemical, Inc.

[0014] The curing agents which may be useful in the present inventionare obvious to persons skilled in the art. Non-limiting examples of thecuring agents include, for example, acid anhydrides. Examples of usefulacid anhydrides include hexahydrophthalic anhydride, methylhexahydrophthalic anhydride (“MHHPA”),methyl-bicyclo[2,2,1]-heptene-2,3-dicarboxylic anhydride (abbreviated as“NMA”; Nadic Methyl Anhydride), succinic anhydride, andhexafluoroisopropylidene-2,2-bisphthalic anhydride, and a mixturethereof.

[0015] The material composition for packaging of the present inventionmay optionally comprise one or more additives well known to personsskilled in the art. Such additives include, for example, a promoter, anantifoaming agent, and an antioxidant.

[0016] The promoters which may be useful in the present invention arewell known to persons skilled in the art. Non-limiting examples of theuseful promoters include the salts, quatemaries, and imidazolates of1,8-diazabicyclo[5,4,0]-undec-7-ene (“DBU”) and a mixture thereof. Thequaternaries useful as promoters are well known to persons skilled inthe art. Non-limiting examples of such quaternaries include benzyltributyl ammonium halides, benzyl trimethyl ammonium halides, benzyltripropyl ammonium halides, phenyl tributyl ammonium halides, tetrabutylammonium halides, triphenyl benzyl ammonium halides, tetraethyl ammoniumhalides, and hexadecyl trimethyl ammonium halides.

[0017] The present invention also pertains to a method of using theabove material composition in packaging light-sensitive components,comprising applying the material composition to the light-sensitivecomponents on a substrate. According to the present invention, thelight-sensitive components include, but are not limited to, imagesensors. Non-limiting examples of the substrates include printed circuitboards and lead frames.

[0018] According to one embodiment of the present invention, thematerial composition for packaging image sensors comprises (a) an epoxyresin selected from the group consisting of an aliphatic epoxy resin, acycloaliphatic epoxy resin, and a mixture thereof and (b) a curing agentselected from the group consisting of acid anhydrides, wherein themixing ratios of said epoxy resin to said curing agent are in the rangeof from 0.7 to 1. 1, preferably 0.85 to 1.0.

[0019] The present invention will be further described in the followingexamples. However, the examples will not make any limitations to thescope of the invention. Any modifications or alterations on theinvention that can be easily accomplished by persons skilled in the artare encompassed in the disclosure of the specification and theaccompanying claims.

EXAMPLES

[0020] The compositions with the formulas as shown in Table 1 below areprepared in accordance with the following procedure: Formula 1 Formula 2Epoxy EPON 828 30 ERL-4221 20 — — EPON1510 10 Curing agent MHHPA 30MHHPA 30 Promoter Quaternary 0.3 Quaternary 0.3

[0021] The epoxy resin, curing agent and promoter are mixed at thepredetermined ratios. The resultant mixture is poured into an aluminumcontainer and baked at 120° C. for one hour. The thickness of thesamples is controlled at about 1 mm. The samples are tested by UVspectrometer for the light transmission rates at the visible range of400˜800 nm (background: air). The results of the test are shown in thefollowing Table 2.

[0022] The epoxy resin, curing agent and promoter are mixed at thepredetermined ratios. The resultant mixture is spin coated onto asilicon wafer. The thickness of the coating is about 5 μm. After beingcured by backing, refractive index of the coating is determined byMETRICON Model 2010 Prism Coupler at the wavelength of 1320 nm. Theresults of the test are shown in the following Table 2.

[0023] The epoxy resin, curing agent and promoter are mixed at thepredetermined ratios. The resultant mixture is poured into an aluminumcontainer and baked at 120° C. for one hour. The thickness of thesamples is controlled at about 1 mm. The samples were tested bypencil-hardness meter for scratch resistance. Moreover, the samples werefurther molded and tested by thermal mechanical analyzer (PE DMA7.0) todetermine their glass transition temperatures. The results of the testsare shown in Table 2 below. TABLE 2 Results of the Tests Formula 1Formula 2 Light transmission >90% >90% Refractive index 1.5342 1.4889Glass transition 125 153 temperature, ° C. Pencil hardness 2H 3H

[0024] It can be concluded from the results in Table 2 that the materialcompositions comprising an aliphatic epoxy resin or cycloaliphatic epoxyresin admixed with a curing agent at the ratio of 0.7 to 1.1 possessgood light transmission rates, low refractive indices, high glasstransition temperatures, and good scratch resistance.

What is claimed is:
 1. A material composition for packaging comprising(a) an epoxy resin and (b) a curing agent, wherein the mixing ratio ofsaid epoxy resin to said curing agent is in the range of from 0.7 to1.1.
 2. The composition of claim 1, wherein the mixing ratio of saidepoxy resin to said curing agent is in the range of from 0.85 to 1.0. 3.The composition of claim 1, wherein said epoxy resin is selected fromthe group consisting of bisphenol A epoxy resin, bisphenol F epoxyresin, an aliphatic epoxy resin, and a cycloaliphatic epoxy resin and amixture thereof.
 4. The composition of claim 1, wherein said epoxy resinis an aliphatic epoxy resin or a cycloaliphatic epoxy resin or a mixturethereof.
 5. The composition of claim 1, wherein said curing agent is anacid anhydride.
 6. The composition of claim 5, wherein said acidanhydride is selected from the group consisting of hexahydrophthalicanhydride, methyl hexahydrophthalic anhydride,methyl-bicyclo[2,2,1]-heptene-2,3-dicarboxylic anhydride, succinicanhydride, and hexafluoroisopropylidene-2,2-bisphthalic anhydride, and amixture thereof.
 7. The composition of claim 1, further comprising apromoter.
 8. The composition of claim 7, wherein said promoter isselected from the salts, quaternaries, and imidazolates of1,8-diazabicyclo[5,4,0]-undec-7-ene, and a mixture thereof.
 9. A methodfor packaging light-sensitive components comprising applying thematerial composition according to any one of claims 1 to 8 to thelight-sensitive components on a substrate.
 10. The method of claim 9,wherein said light-sensitive components are image sensors.
 11. Themethod of claim 9, wherein said substrate is a printed circuit board orlead frame.
 12. A material composition for packaging an image sensorcomprising (a) an epoxy resin selected from the group consisting of analiphatic epoxy resin and a cycloaliphatic epoxy resin and a mixturethereof (b) a curing agent selected from acid anhydrides, wherein themixing ratio of said epoxy resin to said curing agent is in the range offrom 0.7 to 1.1.
 13. The composition of claim 12, wherein the mixingratio of said epoxy resin to said curing agent is in the range of from0.85 to 1.0.
 14. The composition of claim 12, wherein said acidanhydride is selected from the group consisting of hexahydrophthalicanhydride, methyl hexahydrophthalic anhydride,methyl-bicyclo[2,2,1]-heptene-2,3-dicarboxylic anhydride, succinicanhydride, and hexafluoroisopropylidene-2,2-bisphthalic anhydride, and amixture thereof.
 15. The composition of claim 12, further comprising apromoter.
 16. The composition of claim 15, wherein said promoter isselected from the salts, quaternaries, and imidazolates of1,8-diazabicyclo[5,4,0]-undec-7-ene, and a mixture thereof.